Amazon delivering KFX format to the Scribe for personal documents may be a sign that the new annotation features of that platform require KFX format. There are some books for sale on Amazon that use reflowable format but are not available in KFX format, for example
Predators I Have Known Kindle Edition with Audio/Video and
That's a Wrap from The Sea of Tranquility. These books do not support Enhanced Typesetting (KFX format) and the listings for those books show "Sticky notes Not Enabled".
I am curious how sticky notes and PDF annotations are actually stored on a Scribe. Regular text annotations for KFX format are stored in a .yjr file in the .sdr folder associated with the book. In the KFX personal documents posted
earlier in this thread the .yjr file associated with the PDF document has a new data structure called "annotation.personal.handwritten_note". Where the text of a regular annotation would appear it instead has the string "cv5GW4xHvSmWMXVPefHzMPQ0". There is no apparent sign of an actual annotation image. Perhaps it is stored elsewhere on the device.